Friction wedge design optimized for high warp friction moment and low damping force

Abstract

A damping system for a rail car truck utilizes friction wedges supported on side springs to damp relative movement between the rail car truck bolster and the side frames supporting it. Each friction wedge has a generally triangular shape with an angle θ defined between a vertical friction surface which bears against a side frame and a sloping friction surface which moves relative to the bolster. The angle θ and the force P of each side spring are defined by Fw W . E = - P 2 · ( cos     ( θ ) +  μ 2  w · sin  ( θ ) ) ( μ 1  w · cos     ( θ ) + μ 1  w · μ 2  w · sin  ( θ ) + μ 2  w · cos     ( θ ) - sin  ( θ ) ) · 2  · a · w w [ b · ( a · w w ) ] V c . W . E = 2 · μ 1  d · P · ( cos     ( θ ) - μ 2  d · sin  ( θ ) ) ( - μ 1  d · cos  ( θ ) + μ 1  d · μ 2  d · sin  ( θ ) + μ 2  d · cos  ( θ ) + sin  ( θ ) )

What is claimed is:  
     
       1. A damping system for a rail car truck having a bolster, a pair of side frames, a plurality of friction wedges damping relative movement between the bolster and the side frames, and a side spring supporting each friction wedge, each friction wedge having a generally triangular shape with an angle θ being defined between a vertical friction surface and a sloping friction surface, the angle θ and the force P of each side spring being defined by the equations          Fw     W   .   E       =         -   P     2     ·       (         cos                   (   θ   )       +            μ     2      w       ·     sin        (   θ   )           )       (           μ     1      w       ·   cos                     (   θ   )       +       μ     1      w       ·     μ     2      w       ·     sin        (   θ   )         +         μ     2      w       ·   cos                     (   θ   )       -     sin        (   θ   )         )       ·       2        ·   a   ·     w   w           [     b   ·     (     a   ·     w   w       )       ]                   V     c   .   W   .   E       =     2   ·     μ     1      d       ·   P   ·       (       cos                   (   θ   )       -       μ     2      d       ·     sin        (   θ   )           )       (         -     μ     1      d         ·     cos        (   θ   )         +       μ     1      d       ·     μ     2      d       ·     sin        (   θ   )         +       μ     2      d       ·     cos        (   θ   )         +     sin        (   θ   )         )                         
       where:  
       Fw W.E  is the required warp friction force—worn—empty;  
       μ 2w  is the slope warp coefficient—max;  
       μ 1w  is the column warp coefficient—max;  
       a is the bearing centers;  
       b is the wheelbase;  
       W w  is the wedge;  
       V c/W.E  is the maximum compression damping force per suspension—empty;  
       μ 1d  is the column damping coefficient;  
       μ 2d  is the slope damping coefficient.  
     
     
       2. The damping system of  claim 1  wherein the angle θ varies between 28° and 32°. 
     
     
       3. The damping system of  claim 2  wherein the force P varies between about 1,350 lbs. and about 7,300 lbs. 
     
     
       4. The damping system of  claim 1  wherein the bolster has a pair of pockets at each end thereof, with each pocket facing a column of a side frame, there being a friction wedge in each pocket. 
     
     
       5. The damping system of  claim 4  wherein each friction wedge is a single wedge element. 
     
     
       6. The damping system of  claim 4  wherein each friction wedge consists of two symmetrical wedge halves.